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Diagnostic circuit and method of testing a circuit

a technology of diagnostic circuit and circuit, applied in the field of diagnostic circuit, can solve problems such as failure of electrical components to function properly, component failure to function properly, and damage to electrical components

Inactive Publication Date: 2015-01-06
DIEHL AKO STIFTUNG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention provides an affordable and effective diagnostic test device for checking control units. This helps to overcome the shortcomings of previous devices and methods.

Problems solved by technology

If, however, current does not flow through the diagnostic circuit when the relay is commanded to close, the sensor notes the absence of that current and reports to a controller (e.g. microprocessor) that the electrical component is not functioning properly.
Unfortunately, an indication of a failure of the electrical component to function properly can occur when a variety of different faults (e.g. an open load, a disconnected wire, and the like) are experienced and / or the electrical component itself is damaged.
Therefore, the technician will have to check a number of different potential problems to determine which electrical component has actually failed, which electrical component needs to be replaced, which leads or connections to check, and the like.
However, the dynamic range of currents in modern appliances is 10 mA to 25 A. Such a wide range of currents is difficult to produce using a current transformer and requires multiple current transformers leading to a complex diagnostic circuit.
In addition, current sensing cannot differentiate between an open load and a defective load.
It is a well-known problem that service technicians have a tendency to automatically replace electronic control units when repairing an appliance.
Unfortunately, most of the replaced electronic control units are not defective.

Method used

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  • Diagnostic circuit and method of testing a circuit
  • Diagnostic circuit and method of testing a circuit
  • Diagnostic circuit and method of testing a circuit

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

[0055]FIG. 3 shows a diagnostic circuit according to the invention following the basic concepts taught in FIGS. 1 and 2 that is ideally suited for lower current loads typically energized by 120 V A / C. In FIG. 3, a filter capacitor C1 is provided for filtering noise. Clamping diodes D1 and D2 are provided for clamping A / C voltages and turning A / C sinusoidal signals into a square wave clamped between 0 and 5 volts. Voltage and current limiting resistors R1, R2, R3 protect the circuit from high currents. Resistors R4 and R5 are provided for current limiting and redundancy. Resistor R6 is also provided for current limiting. The load LOAD represents a control unit of an appliance or the unit under test. Three connection points A, B and C are shown, two connection points A and B are for connecting the diagnostic circuit to the appliance, specifically an A / C source line L1 and the load LOAD. An internal connection C is the connection to A / C neutral N. The diagnostic circuit measures all re...

second embodiment

[0059]FIG. 4 shows the diagnostic circuit in which loads LOAD 1 and LOAD 2 can be multiplexed and in which only one micro-controlled A / D device MICRO is needed. In addition, for simplicity FIG. 4 omits protective devices such as current and / or voltage limiting resistors and capacitive filters. In FIG. 4, two pull-up resistors R10, R12 are connected between a respective load LOAD 1, LOAD 2 and a 5 volts source. Between each load LOAD 1, LOAD 2 and the one micro-controlled A / D device MICRO is a resistor R11, R13, respectively. Table III shows the expected voltage results to be seen at the input IN.

[0060]

TABLE IIILoad ConnectionVoltage Seen at INLoad 1 connected2.1 voltsLoad 2 connectedLoad 1 Open2.5 voltsLoad 2 ConnectedLoad 1 Connected1.67 volts Load 2 OpenLoad 1 Open  5 voltsLoad 2 Open

[0061]From Table III it is easy to ascertain voltage ranges to determine pass and fail criteria for the loads. For example, a voltage greater than 4.5 volts indicates that both loads failed, a voltage...

third embodiment

[0062]FIG. 5 shows a simplified diagnostic circuit suited for higher current loads typically energized by 240 V A / C such as heater loads. The test circuit of FIG. 5 is ideally suited for sensing high current, lower ohm loads connected to a 240 V A / C source. In FIG. 5, the diagnostic circuit has connection points E, F, G and H for connecting to the load LOAD and to the A / C lines L1 and L2 of the appliance under test. Two relays RELAY 2 and RELAY 3 connect the A / C lines L1 and L2 to the load LOAD. Two pull down resistors R20 and R21 connect the load to ground. As in FIG. 1, the power connections are configured such that D / C ground equals or is connected to A / C neutral N (e.g. a common ground). The micro-controlled A / D device in this instance has two inputs IN1 and IN2. The pull down resistors R20 and R21 connected to the inputs IN1 and IN2 ensure a low reading with no connections. It is further noted that a digital input can be used in place of the A / D inputs. In FIG. 5 it is assumed ...

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PUM

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Abstract

A diagnostic circuit for trouble shooting electronic control units of appliances includes a voltage sensing and signal generation device with an input / output and an input. The circuit includes first terminals for connecting to the load and second terminals for connecting to the two lines of the sinusoidal source. One of the first terminals is connected to the input / output, and another one of the first terminals is connected to the input. A relay is connected between one of the second terminals and the input / output. Another relay is connected between another one of the second terminals and the input. A first diode pair with clamping diodes is connected to the input / output, and a second diode pair first diode pair with clamping diodes is connected to the input.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This is a continuation-in-part application of application Ser. No. 13 / 166,299, filed Jun. 22, 2011, which is a divisional application of application Ser. No. 12 / 039,209, filed Feb. 28, 2008; the prior applications are herewith incorporated by reference in their entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to a diagnostic circuit and more specifically to a diagnostic circuit for trouble shooting electronic control units of appliances.[0004]2. Description of the Related Art[0005]Current sensing diagnostic circuits are often used in appliances (e.g. refrigerators) to monitor the operation of electrical components such as, for example, control units of the appliance. During testing, a current should flow when a controlled relay is commanded to close, and a sensor detects that current and reports that the electrical component being tested is operating as intended. If, however, current does not f...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G01R31/02G01R31/08G01R31/50
CPCG01R31/2844G01R31/024G01R31/2825G01R31/50
Inventor ALVORD, ROBERTKOPEC, JAMESAICHER, JOCHENNGUYEN, VU
Owner DIEHL AKO STIFTUNG